After Rebuilding a Linux System I decided to see if I could add another distribution to it. I was short of space on the hard drive, but I had a 250GB SSD. Unfortunately, on opening up the computer I could not see an easy way to connect the drive internally. I did, nowever, have an external SSD case with a USB 3.0 connection, so I put the drive in there and connected it to a USB 3.0 port on the computer. Then I booted from the netinst iso for Debian 11. I set the root (/) partition on the new USB ssd, but used the same swap and /home partitions I had created for Ubuntu. I could not see any reason not to use the same swap partition and I am guessing that since Ubuntu and Debian are quite similar it will possible to share /home. We will see….

In the old days (about 20 years ago) SCSI disks in Linux system were identified as /dev/sda, for the first disk, /dev/sdb for the second, /dev/sdc for the third, etc. This could be difficult if you have a lot of disks, or if you have removable media. Today’s /dev/sdb might become tomorrow’s /dev/sdd after a reboot in the morning. The solution is to use UUIDs for each partition, assigned when it is created. This is now used in /etc/fstab, so you don’t have to worry about dev/sdb becoming /dev/sdc. This is fine, as long as /etc/fstab uses the correct UUIDs, which your installation program should manage.

The installation went well, and afterwards it rebooted with quite satisfactory speed. I then started the same post-install process that I use for Ubuntu systems, starting with sudo apt install install grub-customizer (Debian, unlike Ubuntu, includes the Synaptic Package Manager out of the box). First check: I get the ominous-sounding error message:

gmcdavid is not in the sudoers file. This incident will be reported.

Apparently this is just how Debian likes to do things. However, unlike Ubuntu, it creates an actual root logon during installation, which you can use to fix this and get your login into the sudoers file:

su -
usermod -aG sudo gmcdavid
exit    

After which I could use sudo just like with Ubuntu. So now I have a system with Windows and two different Linux distributions. GRUB is working fine with all three operating systems.